It can actually be developed.
1. Try to disable self-censoring and just say without thinking (TAKES TIME)
2. Read, listen to and watch funny things, it will rub off.
3. Disable your seriousness. You ain't funny when you can't make fun of yourself.
4. Being mildly drunk helps point 1 & 3.
5. Think "what would Joey have done?"
6. Dump political correctness. It sucks.